Refractory article.



UNITED STATE s PATENT OFFICE.

FRANK J. TONE, OF NIAGARA FALLS, NEW YORK, ASSIGNOR TO THE CARBORUNDUM COMPANY OF NIAGARA FALLS, NEW YORK, A CORPORATION OF PENNSY LVAN IA.

' REFRACTORY ARTICLE.

No Drawing.

To all whom it may concern:

Be it known that I, FRANK J. TONE, a citi zen of the United States, residing at Niagara Falls, in the county of Niagara and State of New York, have invented a new and useful Improvement in Refractory Articles, of which the follow-ing is a full, clear, and exact description.

My invention relates to refractory articles which contain graphite and zirconia. Graphite has long been used in the making of refractory articles, especially crucibles for the melting of metals. I have discovered that a mixtureof graphite, zirconia and a suitable binder, such as clay produce a cruci-- ble of very superior refractory qualities. Such a mixture is very easy to mold and work in the plastic state, and after burning has a body which is very refractory, less oxidizable than the graphite crucible, of superior strength, and of high heat conductivity and great durability.

k zirconia which I prefer to use preferably calcined, sintered or As a typical mixture which may be employed for the production of articles embodying my invention, I take graphite 40 parts; zirconia 40 parts; and plastic clay 20 arts; these proportions being by weight.

hegraphite may be natural flake or Ceylon graphite, or artificial graphite made in the electric furnace. It is preferably crushed material of a fineness that will pass through about a No. 16 mesh. The form of is a natural zirconium oxid analyzing approximately zirconium oxid 80%, silica 15% with small amounts of impurities such as titanium oxid, alumina and iron oxid. This product is shrunk in the electric furnace and then crushed so that all of the product will pass through a screen having 40 meshes to the inch. The clay is preferably a good refractory grade of plastic clay, properly weathered or aged by mechanical means and analyzing about as follows:

Ign.loss 11.00 Silica 56.00 Alumina 26.00 Iron oxid 5.00 A1kalis 1.50

I do not limit myself to this particular clay however, as many clays of varying comositions will act as satisfactory binders.

urthermore, I do not limit myself to any Specification of Letters Patent.

' the side of the Patented Dec. 31, 1918.

Application filed July 26, 1918. Serial No. 246,871.

exact size in the crushing of the zirconia or the graphite, and I have found much finer ades of zirconia to give satisfactory results. Nor do I limit myself to any exact proportions. The clay may be varied to obtain more or less refractory compositions, or compositions which soften at different temperatures, depending on the metal to be melted or the use proposed. These materials are mixed with water and thoroughly worked in a pug mill until full plasticity of the mixture is developed. 1 In the making of crucibles the well known form of crucible jigger is employed in the molding operations, in which a plaster mold conforming to the outside dimensions of the crucible is revolved on the head of the jiggen. A batch of the mixture is put in the mold and an inside forming tool is brought down within the mold ,and presses the material against mold at the same time spinning and working the material and forming it to. shape against the walls of the mold as the mold revolves. The crucibles are then removed from the molds, dried and fired in kilns in the usual manner.

In the manufacture of graphite crucibles the graphite particles or flakes have a tendency to aid in forming cleavages or part ing planes in the walls of the crucible during the molding operation as the material is worked and spun under the forming tool. The weak spots in the structure may not appear'until the crucible is fired and often not until after it has been in use for some time. I find that the addition of the zirconia avoids this defect, that the mixture coheres much more strongly, and that there is no tendency for it to form slipping planes along which pieces of the crucible might spall off when put into use. On the contrary there is produced a very strong homogeneous structure. a

The invention may be applied to many other refractory articles such as muflles, retorts, bricks, tubes, and the like.

The refractory articles produced by my process have many advantages over those produced by clay. and graphite alone, especially when employed for metals which absorb carbon. The cruci les made by this process are specially adapted for the melting of iron and steel; they will withstand sudden change's'of temperatur very successfully without cracking or spalf the meltin o ing. This is a very marked weakness of ordinary graphite crucibles. The heat conductivity of my composition is very high, which means great fuel economy and ease of melting. Zirconia is not subject to oxidization as is graphite and the resistance of the composition to oxidization is therefore relatively high. The tensile strength is greater than that of ordinary graphite articles and it also resists abrasion very successfully.

I do not limit myself to the sole use of clay as a binding material, as other materials will be found of special value in the specific cases.

I claim:

1. A refractory article containing graphite, zirconia and a binder.

2. A refractory article containing graphite, zirconia and clay.

3. A refractory article containing graphite, fused zirconia and a binder.

In testimony whereof, I have hereunto set my hand.

FRANK J. TONE 

